A vehicle-use communication system is in practical use in which locking or unlocking of a vehicle door is achieved without the use of a mechanical key. Specifically, such systems in practical use include: a keyless entry system in which locking or unlocking of a vehicle door is achieved by wireless remote operation by using a portable device carried by a user; and a smart entry (registered trademark) system in which a vehicle door is unlocked when a user carrying a portable device merely approaches the vehicle or merely grips the door handle.
Further, a vehicle-use communication system is also in practical use in which engine start in a vehicle is achieved without the use of a mechanical key. Specifically, a smart start system is in practical use in which the engine is started when a user carrying a portable device merely pushes an engine start button.
In the communication systems described above, the in-vehicle device performs communication with the portable device by using radio signals so as to perform authentication and, after that, perform control concerning the given operation of unlocking, locking, engine start, or the like. However, for the purpose of preventing unauthorized operation, before the operation is executed, it is checked that the portable device is located at a given position. As methods of checking the position of the portable device, methods described in Japanese Patent Publication No. 4483236, Japanese Patent Publication No. 4673234 and Japanese Patent Publication No. 4673230 or the like are known.
Japanese Patent Publication No. 4483236 discloses a position detection method in which a signal is transmitted from an inside-the-vehicle-cabin antenna and an outside-the-vehicle-cabin antenna to the inside and the outside of the vehicle cabin and then the position of the portable device is determined on the basis of which signal triggers a response from the portable device.
Japanese Patent Publication No. 4673234 discloses a keyless entry apparatus in which a portable device receives signals transmitted from a plurality of antennas provided in a vehicle and then the position of the portable device is determined on the basis of the received signal strengths of the signals received by the portable device. The in-vehicle device according to Japanese Patent Publication No. 4673234 stores, in advance, data required for determination of the position of the portable device. Specifically, the portable device is arranged at a plurality of locations along the inner side of the vehicle cabin inside-outside boundary and then the portable device receives signals for received signal strength measurement (for portable device position determination) transmitted from the plurality of transmitting antennas connected to the in-vehicle device so as to measures the received signal strengths of the signals. Similarly, the portable device is arranged at a plurality of locations along the outer side of the vehicle cabin inside-outside boundary and then the portable device receives signals for received signal strength measurement transmitted from the plurality of transmitting antennas connected to the in-vehicle device so as to measures the received signal strengths of the signals. Then, the in-vehicle device stores in advance: the vehicle-cabin inside data group containing a plurality of received signal strengths measured in a state that the portable device follows the inner side of the vehicle cabin inside-outside boundary; and the vehicle-cabin outside data group containing a plurality of received signal strengths measured in a state that the portable device follows the outer side of the vehicle cabin inside-outside boundary.
At the time of operation of the keyless entry system, the portable device measures the received signal strengths of the signals transmitted from the plurality of transmitting antennas and then transmits the measured received signal strengths to the in-vehicle device. The in-vehicle device receives the received signal strengths transmitted from the portable device and then, on the basis of the Mahalanobis distance, determines whether the received signal strengths measured by the portable device are closer to the vehicle-cabin inside data group or the vehicle-cabin outside data group. If the received signal strengths are closer to the vehicle-cabin inside data group, the in-vehicle device determines that the portable device is within the vehicle cabin. Further, if the received signal strengths are closer to the vehicle-cabin outside data group, it is determined that the portable device is located in the outside of the vehicle cabin.
Japanese Patent Publication No. 4673230 discloses a keyless entry apparatus having a similar configuration to Japanese Patent Publication No. 4673234. In the keyless entry apparatus according to Japanese Patent Publication No. 4673230, movement of a door mirror provided in the vehicle affects the signal transmitted from the transmitting antenna so that the received signal strength measured by the portable device varies. Thus, the keyless entry apparatus stores individual first data groups each obtained by measurement in a state that the portable device is arranged along the inner side of the vehicle in a situation that the door mirror is opened or closed.
Similarly, the keyless entry apparatus stores individual second data groups each obtained by measurement in a state that the portable device is arranged along the outer side of the vehicle in a situation that the door mirror is opened or closed. The keyless entry apparatus detects the open-or-closed state of the door mirror. Then, when the door mirror is opened, whether the portable device is within the vehicle cabin is determined by using the first data group and the second data group obtained in a situation that the door mirror is opened. When the door mirror is closed, whether the portable device is within the vehicle cabin is determined by using the first data group and the second data group obtained in a situation that the door mirror is closed.
However, in order that the position determination of the portable device may be accurately performed by using the method of Japanese Patent Publication No. 4483236, the physical strengths of the signals transmitted from the inside-the-vehicle-cabin antenna and the outside-the-vehicle-cabin antenna are required to be adjusted such that the outside and the inside are clearly distinguished on the vehicle cabin inside-outside boundary of the vehicle. This causes a problem of physical difficulty in the adjustment.
In order that a situation may be avoided that the keyless entry apparatus performs erroneous detection of the position of the portable device and hence locking or unlocking of the door is erroneously performed, leakage of a signal from the inside-the-vehicle-cabin antenna to the outside of the vehicle cabin is required to be suppressed as much as possible. However, there is a tendency that the signal from the inside-the-vehicle-cabin antenna leaks through the glass portion of the vehicle door to the outside of the vehicle cabin, and adjustment of this is difficult.
Further, in Japanese Patent Publication No. 4673234, the position determination of the portable device is performed by using the vehicle-cabin inside data group and the vehicle-cabin outside data group of the received signal strengths measured by a method that the portable device is arranged along the inner side and the outer side of the vehicle cabin inside-outside boundary. However, a problem that the signal from the transmitting antenna partly leaks through the glass portion of the vehicle door to the outside of the vehicle cabin is not allowed to be resolved. Thus, erroneous position determination of the portable device may occur.
Further, in Japanese Patent Publication No. 4673230, even when the position of the door mirror, the seat, the steering wheel, or the like varies, the position of the portable device is allowed to be accurately determined. Yet, the problem that the signal from the transmitting antenna partly leaks through the glass portion of the vehicle door to the outside of the vehicle cabin is not allowed to be resolved. Thus, erroneous position determination of the portable device may occur.
Further, also in each of Patent Japanese Patent Publication No. 4483236, Japanese Patent Publication No. 4673234 and Japanese Patent Publication No. 4673230, in a case that the condition for determining that the portable device is within the vehicle cabin is set strict, for example, a trouble is caused that despite that the portable device is actually within the vehicle cabin, the portable device is erroneously determined as being located in the outside of the vehicle cabin so that the engine is not started. In contrast, in a case that the condition for determining that the portable device is within the vehicle cabin is set loose, for example, a trouble is caused that despite that the portable device is actually located in the outside of the vehicle cabin, the portable device is erroneously determined as being within the vehicle cabin so that the locking of the door is released from the outside of the vehicle.
An object of the present patent application is to provide: a vehicle-use communication system in which in the position determination of a portable device performed such that the portable device receives signals transmitted from a plurality of antennas provided on a vehicle side and then the position determination is achieved on the basis of the received signal strengths of the signals measured by the portable device, even when an influence is caused by a signal partly leaking from the inside of the vehicle cabin through a portion of the vehicle to the outside of the vehicle cabin, a situation is allowed to be avoided that the portable device actually located in the outside of the vehicle cabin is erroneously detected as being within the vehicle cabin, and further the portable device within the vehicle cabin is allowed to be reliably detected; an in-vehicle device and a portable device constituting the vehicle-use communication system; and a computer program.